Guide wires are used in various procedures in both the coronary regions and the peripheral regions of the body. For example, guide wires of a very small diameter, for example, on the order of 0.010 to 0.018 inches (0.26 to 0.46 mm), may be suitable for use in narrow coronary vessels. Such guide wires may have an extremely floppy distal tip which may be bent or preformed by the physician to facilitate placement of the guide wire at the desired location. Guide wires come in a range of sizes in addition to those discussed above.
Some of the characteristics preferred in guide wires by physicians include strength, the ability to provide a track for a balloon or other device to advance over and good torsional transmittance.
The size of the guide wire often affects the size and usefulness of devices used in conjunction therewith. For example, guide wires can be used in conjunction with dilation balloons used to perform angioplasty. One type of dilation catheter is referred to as an "over-the-wire" (OTW) catheter. An OTW catheter is one in which a guide wire lumen is provided in the catheter so that a guide wire can be used to establish the path through the stenoses. The dilation catheter can then be advanced over the guide wire until the balloon on the catheter is positioned within the stenoses.
There has been a continuing effort to reduce the profile and shaft size of the catheter so that the catheter can not only reach but also cross a very tight stenosis. Often this results in decreasing the diameter of the guide wire lumen of the catheter. In addition, the guide wire lumen as well as other parts of the catheter are made from polymers which allow a decrease in the wall thickness of the components while still providing the structural and mechanical characteristics needed. Portions of the guide wire may also be made from polymers. The polymer components on the guide wire may make intimate contact with the polymer generally used for the guide wire lumen of the catheter. This contact becomes greater as the difference between the two dimensions, the outer diameter of the guide wire and the inner diameter of the catheter lumen, decreases. The increasing surface contact and resulting polymer on polymer interactions can increase frictional resistance. Several attempts have been made to reduce friction between the guide wire and the guide wire lumen such as coating the exterior of the guide wire and/or the interior of the guide wire lumen with friction reducing materials such as TEFLON. See, U.S. Pat. Nos. 4,884,567 (Engelson) and 4,534,363 (Gold). Helical coils have also been used to reduce friction while providing greater flexibility and control. See U.S. Pat. Nos. 3,731,671 (Mageoh); 3,749,086 (Kline et al.) and 3,973,556 (Fleischhacker et al.). Other approaches can be found in U.S. Pat. Nos. 4,579,127 (Haacke) and 4,430,083 (Ganz et al.)
Accordingly, it is an object of the present invention to provide a guide wire that reduces the amount of contact between the guide wire and the guide wire lumen wall of a catheter used in conjunction with the guide wire.